POTENTIAL INCREASE IN NUTRIENT REQUIREMENTS OF PINUS RADIATA UNDER INTENSIFIED MANAGEMENT

Only limited information is available in New Zealand on the effect of intensified forest management practices on nutrient status and potential fertiliser requirements of Pinus radiata forests. Projections must therefore use the substantial overseas literature. Projections are made of nutrient depletion under a variety of management practices, such as waste and commercial thinnings, in addition to the final harvest. Owing to the limitations imposed by the information available, only provisional conclusions could be drawn. However, intensification in management through shorter rotations, closer utilisation, slash burning and windrowing must greatly increase nutrient removal particularly when two or more of these practices are used in conjunction. Other features of intensive management, such as thinning, clearfelling per se, and bedding in site preparation, have much smaller effects. Referring to nitrogen specifically, sufficient reserves and inputs are generally available for the next crop at present but, with intensified manage­ ment, productivity will only be maintained through substantial fertilisation.

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